The present invention relates to a media drive, a processing method for recording data onto a medium, a processing method for data read from a medium, and a method for controlling a process for reading data from a medium, and more particularly to a magnetic disk recording/reproducing apparatus.
Various devices using optical disks, magnetic tapes, and other media are known as information recording/reproducing apparatus devices. Among others, a hard disk drive is now widely used as a storage device for use with a computer and considered an essential storage device for a present-day computer system. Due to its excellent characteristics, the hard disk drive have found an increasingly wide range of applications, including not only a computer but also a motion picture recording/reproducing apparatus, a car navigation system, a removable memory for use with a digital camera, and the like.
A magnetic disk or other recording medium for use with a hard disk drive contains a plurality of concentric tracks. Each track is divided into a plurality of sectors. Each sector stores the sector's address information and user data. A head of the hard disk drive accesses a target sector in accordance with the sector's address information so that data can be written into the sector and read from the sector.
In a process for reading a medium, for instance, data may not accurately be read at all times. If the hard disk drive cannot accurately read data in a normal read mode, it initiates a recovery procedure. The recovery procedure changes a parameter for a read process and then retries a read. The retry operation is repeated while the parameter value is varied. The retry operation terminates if the data cannot accurately be read after it has been repeated a predetermined number of times. The parameter to be changed may be, for instance, a head position, an amplifier gain for A/D conversion on a channel, or a digital filter parameter value.
In a conventional hard disk drive, parameter changes for a retry operation are made according to pre-established rules. For example, the parameter change rules are determined as described below. For a first retry operation, the first parameter is changed by a specified amount. For a second retry operation, the second parameter is changed by a specified amount. To reduce the number of retry operations, a conventional, typical recovery procedure uses statistical data.
In an assurance test for an outgoing inspection, for example, a retry operation is repeated while all the parameter values are varied to acquire statistical data about the retry count. When retry conditions under which an accurate read operation is performed with a statistically high probability are used initially for recovery procedure execution purposes, it can be expected that the retry count may be decreased to a certain extent. However, the optimum read conditions vary with the write conditions for a data write into the target sector. Therefore, it is difficult for the above retry control, which is based on statistical data, to produce a satisfactory effect.
If, on the other hand, the recovery procedure concludes that a target sector is defective, the data in that sector is rewritten in a spare area of the magnetic disk. The spare area has a plurality of spare sectors for storing user data in place of a defective user sector. A defective sector is reassigned to one spare sector. Spare sector management is exercised by referencing a management table, which is called a defect map.
Various data registration methods are proposed for the use of a defect map (refer, for instance, to Japanese Patent Laid-open No. 2002-268829. Typically, the defect map has data that associates defective sector numbers with spare sector numbers. In a process, for instance, for generating CHS numbers (cylinder number, head number, and sector number), which constitute the parameter information for specifying a sector position from a logical address for a data read, firmware references the defect map so that a logical address corresponding to a defective sector is converted to a corresponding spare address. A spare sector can then be accessed using the logical address corresponding to the defective sector.
If a predetermined retry count is exceeded for data read purposes, the target sector is generally classified as defective so that a spare process is performed. However, spare sectors are formed in an area different from an area for normal user sectors. Therefore, spare sectors are accessed with a delay so as to lower the read/write transfer rate of the hard disk drive. This may result, for instance, in a decrease in the data read speed and deterioration in display quality for motion picture playback.
If a retry operation needs to be repeated multiple times due to incompletely recorded data, the problem may be attributable to a defect in the employed medium or data write conditions such as the temperature and head position for a data write. If the problem is caused by such data write conditions and not caused by the employed medium, spare sectors, which are held in reserve for a specific purpose, are used by an unnecessary spare process although the medium itself has no problem at all.